During an inflammatory response peripheral blood leukocytes, consisting of neutrophils and monocytes, bind to and migrate thru the vascular endothelial cell layer and cross the basement membrane in response to chemotactic factors, and enter the infected tissue where they are effective at controlling or ridding the organism of the infection. When a host defense system responds properly to an infection, the inflammatory response is tightly controlled such that leukocytes enter only the infected area, and consequently do not damage healthy tissue. In certain disease conditions, particularly sepsis, leukocyte action is not tightly controlled, and consequently can cause extensive vascular damage arising as a result of the release of oxygen-derived free radicals, as well as proteases and phospholipases from the neutrophils which thus can cause significant cellular and tissue injury. Harlan, J. M., 1987, Acta Med Scand Suppl., 715:123; Weiss, S., 1989, New England J. of Med., 320:365. For example, sepsis associated neutrophil-mediated endothelial injury has been linked to loss of vascular integrity, thrombosis, and tissue necrosis.
The initial event that leads to neutrophil damage of endothelial cells is the adhesion of neutrophils to the endothelial cell surface. In significant part this is medicated by cellular adhesion molecules associated with the neutrophils that cause them to bind to the endothelial cell surface. The neutrophil adhesion molecules bind to a molecule on the surface of endothelial cells termed ICAM-1 (Intercellular Adhesion Molecule 1). To date, a partial list of the adhesion molecules that have been identified that are involved in this reaction are lymphocyte function-associated antigen-1 (LFA-1), macrophage antigen-1 (MAC-1), also termed MO-1, OKM-1 and complement receptor type-3 (CR-3), and p150,95, also termed complement receptor type-4 (CR-4) and Leu M-5. These molecules collectively have been termed the LFA-1 family, leukocyte adhesion proteins, leuCAM, and the leukocytes integrins. All three molecules are .alpha.-.beta. heterodimers. The .beta. subunit is identical in the three molecules, while the .alpha. subunit differs. Kurzinger, K., and Springer, T. A., 1982, J. of Biol. Chem., 257:12412; Sanchez-Madrid, F., et al., 1983, J. Exp. Med., 158:1785; Trowbridge, I. S., and Omary, M. B., 1981, PNAS (USA), 78:3039.
The three leukocyte integrins are predominately expressed by immune cells. For instance, LFA-1 is found on virtually all immune cells. Kurzinger, K. and Springer, T. A., supra. MAC-1 is expressed by monocytes, macrophages, granulocytes, large granular lymphocytes, and immature and CD-5+B cells. De La Hera, A., et al. 1988, Eur. J. of Immun., 18:1131. p150,95 protein shares the same cell type distribution as MAC-1, but is further expressed by activated lymphocytes, as well as hairy cell leukemia. It is a marker of the latter disease. Schwarting, R., et al., 1985, Blood, 65:974; Miller, B. A., et al., 1985, J. of Immun., 134:3286.
Studies have implicated the leukocyte integrins in cellular adhesion events. For example, LFA-1 is involved in antigen-dependent and antigen-independent interactions of immune cells. Springer, T. A., et al., 1987, Annual Review Immun., 5:223; Martz, E., 1986, Hum. Immunology, 18:3. Most telling are studies utilizing a monoclonal antibody to LFA-1, which have revealed that binding to LFA-1 by monoclonal antibody partially or totally inhibits T lymphocytes adherence to endothelial cells (Mentzer, S. J., et al. 1986, J. of Cell Physiol., 126:285), fibroblasts (Dustin, N. L., et al., 1986, J. of Immun., 137:245), epidermal keratinocytes (Dustin, N. L., et al., 1988, J. of SubBiology, 107:321), and hepatocytes (Roos, E., and Roossien, F., 1987, J. of SubBiology, 105:553).
The role of MAC-1 in cellular adhesion was initially demonstrated also using monoclonal antibodies. Such studies show that MAC-1 binds to C3bi-coated erythrocytes, and that such binding could be inhibited by monoclonal antibodies to MAC-1. Beller, B. I., et al., 1982, J. of Exp. Med., 156:1000. Additionally, MAC-1 has been shown to be involved in macrophage binding to Leishmania Promastigotes, E. coli, and Histoplasma Capsulatum. Mosser, D. and Edelson, P., 1985, J. of Immun., 135:2785; Wright, S. and Jong, M., 1986, J. of Exp Med., 164:1876; Bullock, W. and Wright, S., 1987, J. of Exp. Med., 165:195. Other studies have shown that MAC-1 is involved in neutrophil and monocyte chemotaxis, as well as adherence to glass and plastic surfaces, and to endothelial and epithelial cell monolayers.
p150,95 is reported to be significantly involved in peripheral blood monocyte adhesion to substrates and endothelial cells, phagocytosis of latex particles, and chemotaxis. Keizer, et al., 1987, Eur. J. of Immun., 17:1317; te Velde, A., et al., 1987, Immunology, 61:261. Further, studies using a monoclonal antibody that is directed to p150,95 have shown it to be utilized in conjugate formation by cytotoxic T lymphocytes.
The studies described above, as well as additional studies suggest that the leukocyte integrins function as general adhesion proteins to effect immune cell function. Further, the studies described above have used monoclonal antibodies directed either to the .alpha. or .beta. subunits of the three integrins. For the most part, these studies have shown the common .beta. subunit to play the predominant role in the adhesion-related functions of these molecules. Recently the cDNA clone that encodes the .beta. subunit of human LFA-1, MAC-1, and p150,95 has been isolated. Kishimoto, T., et al., 1987, Cell, 48:681; and Law, S. K. A. et al., 1987, EMBO J., 6:915-919.
As mentioned above, inflammation is a significant part of an organism's defense to infection and may be a cause of injury of extravascular tissue. Moreover, in certain instances there is an uncontrolled inflammatory response, such as that observed in septic shock, which may contribute to the pathogenesis of the disease. Leukocytes have been implicated as being, at least in part, responsible for the damage associated with acute ischemic shock by releasing reactive oxygen metabolites, proteases, and phospholipases at the disease sites. This is supported by studies which have shown that animals depleted of peripheral blood leukocytes show significantly reduced damage from myocardial ischemia and reperfusion. Further, reperfusion injury can be minimized by in vivo administration of MAC-1 monoclonal antibodies. Finally, a rabbit model of hemorrhagic shock and resuscitation reveals that monoclonal antibodies against the .beta. subunit of MAC-1 exhibited a protective effect to liver and the asternal intestinal track. Simpson, et al., J. of Clinical Invest., 1988, 81:624; Vedder, N. and Harlan, J., 1988, J. of Clinical Invest., 81:676. Taken together, these results suggest significant therapeutic value for reagents that block the adhesion of leukocytes via the three leukocyte integrins in controlling tissue and organ injury resulting from a number of disease situations including myocardial infarction, hemorrhagic shock, and other events that cause ischemia that are followed by reestablishing normal circulatory blood flow.
Finally, it is noteworthy that ICAM-1, the endothelial cell receptor for integrin binding, is also the receptor for rhinovirus binding. Staunton, D., et al., 1990, Cell, 61:243. Rhinovirus is a member of the picornavirus family and is responsible for about 50% of common colds. Sperber, S. and Hayden, F. (1988) Antimicrob. Agents Chemother. 32, vol. 409, page 32. A prophylactic approach to preventing the common cold is to interfere with the binding of rhinovirus to cell bound ICAM-1. Indeed, a soluble form of ICAM-1 has recently been reported to be effective. Marlin, S. D., et al., 1990, Nature, 344:70.